There is a global lack of knowledge on tropical ecotoxicology, particularly in terms of mangrove areas. These areas often serve as nurseries or homes for several animal species, including Ucides cordatus (the uçá crab). This species is widely distributed, is part of the diet of human coastal communities, and is considered to be a sentinel species due to its sensitivity to toxic xenobiotics in natural environments. Sublethal damages to benthic populations reveal pre-pathological conditions, but discussions of the implications are scarce in the literature. In Brazil, the state of São Paulo offers an interesting scenario for ecotoxicology and population studies: it is easy to distinguish between mangroves that are well preserved and those which are significantly impacted by human activity. The objectives of this study were to provide the normal baseline values for the frequency of Micronucleated cells (MN‰) and for neutral red retention time (NRRT) in U. cordatus at pristine locations, as well to indicate the conservation status of different mangrove areas using a multi-level biological response approach in which these biomarkers and population indicators (condition factor and crab density) are applied in relation to environmental quality indicators (determined via information in the literature and solid waste volume). A mangrove area with no effects of impact (areas of reference or pristine areas) presented a mean value of MN‰<3 and NRRT>120min, values which were assumed as baseline values representing genetic and physiological normality. A significant correlation was found between NRRT and MN, with both showing similar and effective results for distinguishing between different mangrove areas according to conservation status. Furthermore, crab density was lower in more impacted mangrove areas, a finding which also reflects the effects of sublethal damage; this finding was not determined by condition factor measurements. Multi-level biological responses were able to reflect the conservation status of the mangrove areas studied using information on guideline values of MN‰, NRRT, and density of the uçá crab in order to categorize three levels of human impacts in mangrove areas: PNI (probable null impact); PLI (probable low impact); and PHI (probable high impact). Results confirm the success of U. cordatus species' multi-level biological responses in diagnosing threats to mangrove areas. Therefore, this species represents an effective tool in studies on mangrove conservation statuses in the Western Atlantic.

Globally, there is a lack of knowledge about tropical ecotoxicology dealing with the potential impact of metal contamination in mangrove ecosystem. This habitat is considered a nursery for several animal species, among them the "uçá"-crab (Ucides cordatus), known as a key species due to its biological and economical importance. This study evaluated the association involving metal contamination (Cd, Cu, Pb, Cr, Mn and Hg) in water, sediment, red-mangrove vegetation (Rhizophora mangle) and tissues of uçá crab, together with its geno-cytotoxic responses, based on micronucleated hemocytes frequency and the retention time of neutral red in lysosomes. We assessed six mangrove areas with distinct pollution levels in São Paulo State, Brazil, where the water and sediment contamination by metals were associated with accumulation of these pollutants in biotic compartments (mangrove leaves and crab). In U. cordatus, metal accumulation was best explained by metal concentration found in leaves of R. mangle than in the water or sediment, indicating that feeding drives metal exposure in this organism. Mercury (Hg) concentration in sediment, copper (Cu) concentration in hepatopancreas of U. cordatus and lead (Pb) in water and green leaves of R. mangle showed a significant correlation with genotoxic impact in U. cordatus. However, copper concentration (in green/senescent leaves and hepatopancreas) and lead (in sediment), were the major metals affecting lysosomal membrane integrity. Therefore, representatives of all compartments were associated with cyto and genotoxicity in this species, thus requiring a holistic approach to issues related to sublethal damage. Probability estimates of cytogenetic impacts related to metal concentration in abiotic compartments (significantly correlated with known biomarkers: Hg in sediment; and Pb in water and sediment) are also presented. Our results highlight the need for environmental restoration of mangroves areas contaminated with metals, responsible for cytogenetic injuries and revealing a pre-pathological condition in this sentinel species, in addition to ecological disturbances.

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